'\" t
.\"     Title: utmpdump
.\"    Author: [see the "AUTHOR(S)" section]
.\" Generator: Asciidoctor 2.0.20
.\"      Date: 2024-12-16
.\"    Manual: User Commands
.\"    Source: util-linux 2.40.4
.\"  Language: English
.\"
.TH "UTMPDUMP" "1" "2024-12-16" "util\-linux 2.40.4" "User Commands"
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.SH "NAME"
utmpdump \- dump UTMP and WTMP files in raw format
.SH "SYNOPSIS"
.sp
\fButmpdump\fP [options] \fIfilename\fP
.SH "DESCRIPTION"
.sp
\fButmpdump\fP is a simple program to dump UTMP and WTMP files in raw format, so they can be examined. \fButmpdump\fP reads from stdin unless a \fIfilename\fP is passed.
.SH "OPTIONS"
.sp
\fB\-f\fP, \fB\-\-follow\fP
.RS 4
Output appended data as the file grows.
.RE
.sp
\fB\-o\fP, \fB\-\-output\fP \fIfile\fP
.RS 4
Write command output to \fIfile\fP instead of standard output.
.RE
.sp
\fB\-r\fP, \fB\-\-reverse\fP
.RS 4
Undump, write back edited login information into the utmp or wtmp files.
.RE
.sp
\fB\-h\fP, \fB\-\-help\fP
.RS 4
Display help text and exit.
.RE
.sp
\fB\-V\fP, \fB\-\-version\fP
.RS 4
Print version and exit.
.RE
.SH "NOTES"
.sp
\fButmpdump\fP can be useful in cases of corrupted utmp or wtmp entries. It can dump out utmp/wtmp to an ASCII file, which can then be edited to remove bogus entries, and reintegrated using:
.RS 3
.ll -.6i
.sp
\fButmpdump \-r < ascii_file > wtmp\fP
.br
.RE
.ll
.sp
But be warned, \fButmpdump\fP was written for debugging purposes only.
.SS "File formats"
.sp
Only the binary version of the \fButmp\fP(5) is standardised. Textual dumps may become incompatible in future.
.sp
The version 2.28 was the last one that printed text output using \fBctime\fP(3) timestamp format. Newer dumps use millisecond precision ISO\-8601 timestamp format in UTC\-0 timezone. Conversion from former timestamp format can be made to binary, although attempt to do so can lead the timestamps to drift amount of timezone offset.
.SH "BUGS"
.sp
You may \fBnot\fP use the \fB\-r\fP option, as the format for the utmp/wtmp files strongly depends on the input format. This tool was \fBnot\fP written for normal use, but for debugging only.
.SH "AUTHORS"
.sp
Michael Krapp
.SH "SEE ALSO"
.sp
\fBlast\fP(1),
\fBw\fP(1),
\fBwho\fP(1),
\fButmp\fP(5)
.SH "REPORTING BUGS"
.sp
For bug reports, use the issue tracker at \c
.URL "https://github.com/util\-linux/util\-linux/issues" "" "."
.SH "AVAILABILITY"
.sp
The \fButmpdump\fP command is part of the util\-linux package which can be downloaded from \c
.URL "https://www.kernel.org/pub/linux/utils/util\-linux/" "Linux Kernel Archive" "."